The Effects of Training Modality on Muscle Strength

Outline

Chapter I: Introduction

1. Physiological Area

Training effects

B.     Rationale

1. Purpose

The study is to compare the different types of training and how it effects the strength of muscles.

D.     Hypothesis

It is hypothesized that eccentric training will result in a stronger muscle than with concentric training.

E.     Key terms

Chapter II: Body

1. Concentric Versus Enhanced Eccentric Hamstring Strength Training: Clinical Implications
   1. Injuries to muscle strength
   2. Hamstring muscle focus
   3. 1 RM changes with training
   4. Isotonic weight training

B.     Effects of Concentric and Eccentric Training on Muscle Strength, Cross-Sectional Area, and Neural Activation

5. Isokinetic training on quadriceps
6. Torque differences in training
7. Neural activation as result of each training

C.     Force and EMG Power Spectrum During Eccentric and Concentric Actions

8. Focus on elbow flexor muscles
9. Motor unit recruitment with different training
10. Force differences with training
11. EMG differences with training

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D.     Knee Flexor and Extensor Strength During Concentric and Eccentric Muscle         Actions After Anterior Cruciate Ligament Reconstruction Using the Semitendinosus Tendon and Ligament Augmentation Device

1. Operated versus nonoperated knees
2. Peak torque and work measurements
3. Stability
4. Activity levels

E.     Concentric Versus Eccentric Isokinetic Strengthening of the Rotator Cuff

5. Gender differences
6. Rotator cuff focus
7. More efficient training
8. Increasing power

Chapter III: Summary/Conclusion

1. Key Concepts
   1. Strength training
   2. Concentric versus eccentric
   3. Metabolic differences

B.     Conclusions

Chapter I: Introduction

Physiological area: Training Effects

Rationale:

There are different types of training techniques resulting in a stronger muscle. Most people believe that working out and going through a daily routine will get them the results they want. What if it wasn’t the reoccurring workout but the type of workout involved? Comparing the different techniques of training and how the muscle if effected will allow for a closer look at what type of training is favored for a stronger muscle. These studies have shown how eccentric, concentric and isometric training techniques have produced different muscle strength results.

In a muscle, certain things happen for a muscle to contract that the human eye cannot see. These contractions happen microscopically and come from the sarcomere, this is where “the magic happens.” When looking at how a muscle contractions and what certain contractions help strengthen that muscle, first look at what is exactly happening for that muscle to contract. In a sarcomere, different components are present to produce a contraction. In a muscle, different muscle fibers are recruited in certain situations. Fast twitch fibers are recruited during anaerobic exercises, while slow twitch fibers, which are recruited first, are recruited during aerobic exercise. These fibers are made of myofibrils which contain the sarcomere. A sarcomere is from Z disc to Z disc, between these discs, actin, tropomyosin and myosin use the sliding filament theory. The sliding filament theory is what explains the contraction of the muscle. During the sliding filament theory, myosin heads form cross bridges that allow the actin to interact and “slide” creating a contraction.

The difference between eccentric and concentric contractions are how each is demonstrated. Eccentric contractions is a contraction that produces force while the muscle is lengthening. An example of this would be the downward motion of a bicep curl. While moving the weight down, the bicep muscles lengthen while producing tension. This movement is hypothesized to result in the most strength produced in the muscle after training. Concentric contractions are defined as a contraction the happens when a muscle is shortening while it produces tension. An example of this would be the contraction during a bicep curl on the way up. Isometric contractions are another contraction that is used as a control group for most studies. (Higbie, 1996). Isometric contractions occur when the muscle does not change in length. An example of an isometric contraction would be a plank exercise where the core muscles are used to keep stable but never actually change in length.

Research performed on sixty women from ages 18-35 years of age were used to see the difference in these training techniques. (Higbie, 1996). Each subject had data collected when performing concentric and eccentric exercises. The muscles used in this experiment were the quadriceps muscles. Cross-sectional area was collected to detect the changes. The cross-sectional area of a muscles are used to show the strength of that muscle because strength and CSA are highly related. The neural activation of the quadriceps was also collected in this experiment to show the activation of the fast twitch and slow twitch fibers in the muscle. The findings in this study is similar to other studies because they found that the  eccentric test group had an increase in strength in comparison to the strength test with the concentric group. “Gains in strength consequent to Con and Ecc training are highly dependent on the muscle action used for training and testing”(Higbie, 1996).Another research experiment was done to men to show their change in strength with different exercises. Twenty-seven healthy men were tested to show the difference in strength training to their hamstring muscles. 1 RM were used to show the difference in strength, each subject did a 1 RM for the hamstring muscle and then returned to do another RM. The difference in the results were that eccentric were very useful in providing more strength in hamstrings. (Kaminski, 1998). These two studies show just a peek at what eccentric muscle contractions can do for subjects whether it be for prevention of injury or rehabilitation. Showing the differences between these contractions and how they affect strength can determine how a physical therapist prescribes exercises for certain injuries. More research needs to be done on how exactly the strength is created, however, studies are becoming more and more prevalent in this field.

Purpose: The study is to compare the different types of training and how it effects the strength of  muscles.

Hypothesis: Eccentric training will result in a stronger muscle than with concentric training.

Key Terms:

Isometric Contraction- a muscle fiber contraction that does not result in a length change in muscle fiber

Concentric Contraction- a dynamic muscle contraction that produces tension during shortening

Eccentric Contraction- a dynamic muscle contraction the produces tension (force) while lengthening

Strength- the ability of a muscle or a muscle group to exert maximal force against a resistance in a single repetition

Hypertrophy- excessive development of an organ or part; specifically :  increase in bulk (as by thickening of muscle fibers) without multiplication of parts

Fast-twitch fibers- fast twitch muscle fibers that perform primarily under glycolytic conditions

Slow-twitch fibers- slow twitch muscle fibers that rely primarily on oxidative metabolism to produce energy

Citations:

Higbie, E. J., Cureton, K. J., Warren III, G. L., & Prior, B. M. (1996, November 1). Effects of concentric and eccentric training on muscle strength, cross-sectional area, and neural activation. Journal of Applied Physiology, 81(5), 2173-2181.

Kaminski, T. W., Wabbersen, C. V., & Murphy, R. M. (1998). Concentric Versus Enhanced Eccentric Hamstring Strength Training: Clinical Implications. Journal of Athletic Training, 33(3), 216–221.

Chapter II: Body

Refereed Journal Article Review #1

1. Reference:

Ellenbecker, T. S., Davies, G. J., & Rowinski, M. J. (1988). Concentric versus eccentric isokinetic strengthening of the rotator cuff: Objective data versus functional test. The American Journal of Sports Medicine, 16(1), 64-69.

2. Purpose:

The purpose of this study was to determine whether eccentric or concentric isokinetic training of the rotator cuff is more efficient in increasing power, as well as determining which would produce greater improvement in a functional test.

3. Methods:
   1. Subjects:
   2. 22
4. Male and female
5. college varsity tennis players
   2. Protocol:
      1. Each tennis player was instructed to hit three serves at maximum capability while being filmed.

2. The participants completed the protocol during a 6 weeks of isokinetic exercise workouts, two times per week.
3. The participants fastest serve was used for digital analysis
4. Then participants had isokinetic pretesting which consisted of concentric internal and external rotation with the glenohumeral joint abducted to 90º
5. Eccentric internal and external rotation was then tested with the glenohumeral joint at 90º abduction
6. The tennis serves before and after training was then compared

3. Instrumentation:
4. Cybex II isokinetic dynamometer
5. UBXT Cybex upper body testing table
6. Kin-Com dynamometer
7. Training Program:
8. 6 weeks of training
9. two isokinetic exercise workouts per week

4. Results:
5. There was a significant strength change from both concentric and eccentric groups
6. the change between concentric strength happened when eccentric work was done.
7. Overall strength after training did not show a huge change in eccentric contractions
8. concentric parameters used provided more strength than the eccentric

5. Conclusions:
   1. if the specific training goal is to enhance the muscle fibers to provide a rapid contraction the isolate the actual contractile muscle fiber with concentric contraction
   2. eccentric testing did not provide significant strength data results.
   3. eccentric and concentric training groups showed increases in torque
   4. skill improvement only happened with concentric training

Refereed Journal Article Review #2

1. Reference:

Higbie, E. J., Cureton, K. J., Warren III, G. L., & Prior, B. M. (1996, November 1). Effects of concentric and eccentric training on muscle strength, cross-sectional area, and neural activation. Journal of Applied Physiology, 81(5), 2173-2181.

2. Purpose:

The objectives of this study were 1) to compare the effects of Con and Ecc heavy-resistance isokinetic training on strength, cross-sectional area (CSA), and neural activation of the quadriceps muscle and 2) to determine the relationship of changes in strength to changes in muscle CSA and neural activation.

3. Methods:
   1. Subjects:
   2. 60

2.Women

3.university student population

1. Protocol:
   1. Each participant was assigned to a concentric and eccentric only training or control group

2. Each participant were involved in four test sessions; orientation, two sessions which involved muscular strength and EMG activity measurements were taken, and a session during which CSA of the quadriceps muscle was assessed by MRI
3. participants performed maximal voluntary concentric and eccentric isokinetic knee extensions at 60º/s
4. three maximal concentric and eccentric isokinetic muscle actions were taken along with EMG activity

1. Instrumentation:
2. EMG
3. MRI
4. ANOVA
5. Kin-Com dynamometer
6. Training Program:
7. 3 days a week for 10 weeks
8. 10 repetitions with no rest

4. Results:
5. there was a large change in eccentric training from pretesting to posttests in average torque
6. eccentric isokinetic training had more change in strength than concentric training
7. Cross sectional area was larger after eccentric training compared to concentric and the control group

5. Conclusions:
   1. Eccentric training improves eccentric contractions and is more powerful than concentric contractions
   2. Concentric training improves both eccentric and concentric contractions
   3. CSA and neural activation was increased with eccentric training
   4. strength in muscle is dependent on training and testing

Refereed Journal Article #3

1. Reference:

Kaminski, T. W., Wabbersen, C. V., & Murphy, R. M. (1998). Concentric Versus Enhanced Eccentric Hamstring Strength Training: Clinical Implications. Journal of Athletic Training, 33(3), 216–221.

2. Purpose:

The goal is to examine the strength gains associated with a traditional, concentrically limited, hamstring strength-training protocol and an enhanced eccentric strengthening program using eccentric loads equal to the concentric IRM value.

3. Methods:
   1. Subjects:
   2. 27

2.Males

3.mean age =22.9 ± 3.1 years

1. Protocol:
   1. Each participant reported for isotonic 1RM and isokinetic strength pretesting on 2 separate occasions.
   2. Participants performed a hamstring curl with their dominant leg.
   3. Participants also performed isokentic knee flexion strength on the KinCom 125 AP isokinetic dynamometer.
   4. Concentric and Eccentric peak torque values at test velocities of 60º/s and 180º/s were used.
   5. Participants performed 3 submaximal and 3 maximal warm up reps with 1 minute rest before performing 3 maximal concentric and 3 maximal eccentric repetitions at each velocity.
2. Instrumentation:
3. Cybex isotonic prone hamstring-curl with Negator eccentric-loading           counterbalance weight system

2.Kin-Com 125 AP isokinetic dynamometer

1. Training Program:
2. 6 week hamstring strength-training program
3. exercise twice each week for 12 training sessions

3.no lower extremity strength training during study

4. Results:
   28. There was improvement with eccentric training by 28.8% while concentric training only improved 19.0%

• eccentric isokinetic PT/BW ratios improved at both 60º/s (improved 37.7%) and 80º/s (22.0%)

1. Eccentric training had more muscle soreness than concentric training.

5. Conclusions:
   1. Just concentric training does not improve eccentric PT/BW ratios
   2. Eccentric isotonic training produced significant improvements while concentric isotonic training created no significant strength gains
   3. most muscle injuries happen during eccentric actions, this may be reduced by eccentric isotonic training for strength

Refereed Journal Article #4

1. Reference:

Komi, P. V., Linnamo, V., Silventoinen, P., & Sillanpaa, M. (2000). Force and EMG power spectrum during eccentric and concentric actions. Medicine & Science in Sports & Exercise, 32(10), 1757-1762.

2. Purpose:

The purpose of this study was to examine the effects of different movement velocities in concentric and eccentric actions on muscle tension, average EMG amplitude, and the EMG power spectrum.

3. Methods:
   1. Subjects:
   2. 9

2.Males

3.18-27 years old

1. Protocol:
   1. Each participant was asked to sit in a chair and have their right supinated forearm fixed to an isokinetic machine
   2. Each participant performed a bicep curl while hooked up to the ergometer
   3. all actions were performed maximally
   4. trials were performed in a random order with two consecutive attempts at each condition and a resting period of 2 minutes between the trials
   5. EMG was recorded from the bicep brachii, brachioradialis, and tricep brachii
2. Instrumentation: ergometer, EMG
3. Training Program: NA

4. Results:
   1. Average force was always greatest in the middle of the contraction
   2. Concentric contractions had a higher velocity and force at a greater angle compared to flexed.
   3. EMG proved greatest in concentric actions when compared to eccentric contractions
   4. EMG recordings of the bicep brachii, brachioradialis, and tricep brachii proved that the bicep brachii had the most activity during all of the angles of the elbow

5. Conclusions:
   1. it is difficult to maintain maximal force for the whole range of motion during an eccentric action
   2. EMG activity and power is on the same level or lower for eccentric contractions than for concentric contractions
   3. Increased muscle lengths associated with eccentric action may explain the reason behind the lower EMG power and velocity
   4. median frequency used to interpret selective recruitment of motor units is yet to be determined.

Refereed Journal Article #5

1. Reference:

Kramer, J., Nusca, D., Fowler, P., & Webster-Bogaert, S. (1993). Knee flexor and extensor strength during concentric and eccentric muscle actions after anterior cruciate ligament reconstruction using the semitendinosus tendon and ligament augmentation device. The American Journal of Sports Medicine, 21(2), 285-291.

2. Purpose:

The purpose of this study was to compare knee flexor and extensor strength measurements of operated and nonoperated knees following ACL reconstruction using the semitendinosus tendon and LAD during concentric and eccentric muscle actions. The secondary purpose was to determine the interrelationships among strength measurements, knee stability and current activity levels.

3. Methods:
   1. Subjects:
   2. 30

2.15 Females and 15 males

3. mean age: 27 ± 8 years
4. Protocol
   1. Each participant underwent a surgery that was used to harvest the semitendinosus tendon through a small incision anteriorly
   2. a composite graft was made and passed through a tibial drill hole along a 6-mm groove in the back of the notch, over the top of the later condyle and secured to the femur
   3. each participants knee was placed in a hinged brace with freedom to move from 30º to 90º for a period of 6 weeks
   4. isokinetic testing was done by each particpant by riding a bicycle ergometer
   5. knee extension testing was done while the participant was seated on the Kin-Com table with hip angle of 80º
   6. each participant completed four maximal concentric-eccentric cycles
5. Instrumentation:

1.ergometer

2.Kin-Com

1. Training Program: physical therapy was used and jogging was allowed at 16 weeks post surgery and sports after 12 months.

4. Results:
5. The men in the study had higher work and torque at all angles.

• men and women had more torque during knee extension compared to knee flexion.

1. men and women also had more work done during knee extension compared to knee flexion.
2. Eccentric values for both men and women produced more work and power done
3. operated knees produced greater anterior displacement compared to nonoperated knee

5. Conclusions:
6. nonoperated knee had significantly greater torque and work done during knee flexion but only during concentric actions.
7. Eccentric strength levels return to normal sooner than concentric strength.
8. men produced a higher peak torque and work done than women in all comparisons but showed signs of similar differences between operated and nonoperated knees.

Chapter III: Summary/Conclusion

Training techniques are very important when trying to gain strength. In past research, eccentric actions have been known to provide the most improvement for strength. This information is most useful when training someone, helping someone recover from an injury, or trying to prevent injury. The mechanisms behind contractions include muscle fibers, sarcomeres, action potentials, and a resulting contraction. Eccentric, concentric and isometric are the training techniques used in these articles. The eccentric contraction is the result of a lengthening muscle fiber. This would be an example of a bicep curl being lowered down. A concentric contraction is the result of a muscle fiber shortening. Isometric contractions are a result of not a shortening or nor a lengthening of a muscle fiber. The muscle fiber length does not change in isometric contractions, like pushing on a wall. The hypothesis that eccentric training produces a stronger muscle than concentric training was tested many ways. Both eccentric and concentric exercises provide strength to the muscle. However, the purpose to find which one is the most beneficial. These articles listed above were tested by many populations. Rehabilitation patients, athletes, women and men were among  the participants involved in these experiments. Men and women tennis players were both tested on the strength in their rotator cuff (Ellenbecker, 1988). Other testing included sixty women of the university student population who were tested on the strength in their quadriceps (Higbie, 1996), twenty-seven males in their mid-twenties were tested on their hamstring strength (Kaminski, 1998). To contrast, nine males between the ages of 18-27 years of age were tested on the strength in their arms, specifically, the bicep brachii, brachioradialis, and tricep brachii (Komi, 2000). Also, there was also a study done that included the research on how training eccentrically versus concentrically helps post ACL reconstruction patients (Kramer, 1993).  These studies had a range of results that included the differences and benefits of training in eccentric or concentric ways. The methods used in each experiment were similar. Each experiment used assigned groups with training assignments which collected data and compared eccentric training to concentric training. In the study done with twenty- two collegiate male and female tennis players, the strength in the rotator cuff was tested by putting the participants through a six week training study which involved  a Cybex II isokinetic dynamometer using a UBXT Cybex upper body testing table, and a Kin-Com dynamometer (Ellenbecker, 1988). Another experiment included sixty women of the student population. In this experiment, participants were given either eccentric or concentric training programs. Each group trained either eccentrically or concentrically three days a week for ten weeks. Their strength along with neural activation in the quadriceps were both collected during this experiment. The contractions were measured using Electromyography, and MRI and also a Kin-Com Dynamometer, like the article mentioned (Higbie, 1996). Hamstring strength was also experimented on by using a training technique. Twenty-seven males were asked to be involved in twelve training sessions along a six week hamstring strength training program that occurred twice each week. The experiment collected data using Cybex isotonic prone hamstring curl with Negator eccentric-loading counterbalance weight system along with a Kin-Com 125 AP isokinetic dynamometer (kaminski, 1998). A reoccurring method with these experiments is the assigned groups and the Kin-Com Dynamometer. The bicep brachii, brachioradialis, and tricep brachii were tested by nine males with an ergometer. Each participants performed a bicep curl maximally with two attempts. Like before, this experiment also used electromyography in the instrumentation to collect data (Komi, 2000). Clinical experiments were done to see the effect of eccentric and concentric training with rehabilitation. In an experiment that involved 15 females and 15 males, participants that had anterior cruciate ligament reconstruction and worked with them using eccentric and concentric contractions in their rehabilitation therapy. Kin-Com and an ergometer was used in this experiment to collect data along a period of six weeks (Kramer, 1993). Eccentric and concentric contraction results were collected and analyzed in each experiments. The results in each experiment are as follows. Some experiments had results that supported the hypothesis, however others did not. There was a significant increase in neural activation and increase in muscle strength in the quadriceps after participants completed an eccentric training program as opposed to a concentric training program( Higbie, 1996). Electromyography showed the contrast between the two exercises in more than one experiment. Another experiment that was used to determine eccentric versus concentric was a test done on the hamstrings. Twenty-seven men were used in an experiment that showed a gain in strength in eccentric contractions. In the article, the results showed an increase of eccentric training by 9.8% difference. This experiment also pointed out that eccentric training can produce more soreness that concentric training. Soreness can occur as acute onset muscle soreness or delayed onset muscle soreness (Kaminski, 1998).  Acute onset muscle soreness occurs during or immediately exercising. Whereas delayed onset muscle soreness occurs after exercising and can worsen within 24-48 hours after exercising. Soreness can hinder an experiment if participants become too sore to finish the training required.  Even though soreness was presented in the experiment that Kaminiski conducted, the training was able to be completed with a result that supported the hypothesis that eccentric training is more beneficial than concentric training. Different training can be used in therapy as well. Physical therapy uses exercise prescriptions to help patients gain strength back after accidents, injuries, surgery, etc. Anterior cruciate ligament reconstruction patients were used in this experiment. ACL patients were post-surgery for about a year and a half. The idea was to have the patients do a training program while in physical therapy that focused on either eccentric or concentric training to see which training program helped them the most. The results were of the operated knee was then compared to the non-operated knee. Eccentric strength gains improved more in comparison to concentric strength gains in the knee. Patients involved in the eccentric training programed also came back with more strength quicker than concentric patients. Torque and work done were greater with eccentric training as well. Knee flexion and extension velocity results improved eccentrically compared to concentrically. Knee flexion velocity was only at 122 degrees per second with concentric training, whereas, eccentric training showed an velocity at 146 degrees per second. Information like this can be very beneficial to physical therapists and occupational therapists because it can help a patient gain more strength and mobility back in the knee that was operated on (Kramer, 1993). Every experiment up to this point supported that eccentric was more beneficial than concentric. However, some experiments showed conflicting results to the hypothesis. Tennis players were tested on how different ways of training effects strength in their rotator cuff. Even though the study showed that eccentric training showed more improvement, the findings were insignificant to the eccentric training group. This is due to the soreness that the participants showed during training. This study supports eccentric having more promise than concentric, however, the more studies in this certain article need to be done due to the insignificant findings. Another study included nine males that performed 1 rep max bicep curl and then measured the velocity and EMG. This study showed results that included a higher EMG activity during concentric contractions than eccentric contractions. The results show how eccentric and concentric contractions can both be used to gain strength but eccentric is more preferred in most studies. More research needs to be done in this area of study to prove that eccentric training has more improvements and can be more beneficial than concentric training.

In conclusion, eccentric training may cause more soreness, but they also cause growth in the cross sectional area, growth in torque and work done, and also growth in strength. More eccentric training needs to be done when exercising to provide more muscle strength. This information can help with people trying to get stronger and it can help physical therapists diagnose exercises to patients. This is the exact reason why physical therapists need to stay up to date on research. To help better the hurt people they are treating.

References

Ellenbecker, T. S., Davies, G. J., & Rowinski, M. J. (1988). Concentric versus eccentric isokinetic strengthening of the rotator cuff: Objective data versus functional test. The American Journal of Sports Medicine, 16(1), 64-69.

Higbie, E. J., Cureton, K. J., Warren III, G. L., & Prior, B. M. (1996, November 1). Effects of concentric and eccentric training on muscle strength, cross-sectional area, and neural activation. Journal of Applied Physiology, 81(5), 2173-2181.

Kaminski, T. W., Wabbersen, C. V., & Murphy, R. M. (1998). Concentric Versus Enhanced Eccentric Hamstring Strength Training: Clinical Implications. Journal of Athletic Training, 33(3), 216–221.

Komi, P. V., Linnamo, V., Silventoinen, P., & Sillanpaa, M. (2000). Force and EMG power spectrum during eccentric and concentric actions. Medicine & Science in Sports & Exercise, 32(10), 1757-1762.

Kramer, J., Nusca, D., Fowler, P., & Webster-Bogaert, S. (1993). Knee flexor and extensor strength during concentric and eccentric muscle actions after anterior cruciate ligament reconstruction using the semitendinosus tendon and ligament augmentation device. The American Journal of Sports Medicine, 21(2), 285-291.